1. Field of the Invention
The present invention relates to a method of, and an apparatus for manufacturing elongate plastic articles, e.g. molding members for automobiles, having a cross-section which varies in the longitudinal direction of the article.
2. Description of the Related Art
A variety of molding members are widely used for automobiles, such as front or rear window molding members, body side molding members, etc. Among others, Japanese Patent Application Laid-open Publication No. 61-135,824 discloses a windshield molding member which includes an upper segment to extend along an upper edge of a windshield plate, a pair of side segments to extend along side edges of the windshield plate, and a pair of corner portions connecting the upper and side segments into an integral component.
In the known molding members mentioned above, the upper and side segments are generally composed of a synthetic resin material extruded into respectively predetermined cross-sections which are basically same with and slightly different from each other. That is, the upper segment includes a main body which is provided with a first lip section to be engaged with the outer surface of a windshield plate, a second lip section to be engaged with the outer surface of a vehicle body panel, and a leg section to be inserted into a gap between the edge of the windshield plate and the body panel. The leg section has fins on both sides to be engaged with the periphery of the windshield plate and the body panel, respectively, so as to prevent undesirable withdrawal of the lip section out of the gap. The upper segment may have an ornamental film and a core element arranged in the main body and the leg section, respectively, depending upon ornamental and/or functional requirements. On the other hand, the side segment has a basic cross-section which is the same as that of the upper segment, as well as an additional cross-section in the form of a ridge on the first lip section, which is adapted to define a weir or channel extending along a side edge of the windshield plate.
The upper segment without the ridge serves to realize a flush outer surface of the automobile body along the upper edge of the windshield plate, while the ridge on the side segment achieves the functions to guide rain water on the windshield plate to flow along the weir or channel, and to thereby, prevent the rain water from flowing onto side windows across the side segment and the neighboring body panel portion (or pillar) to disturb the driver's sight through the side windows.
In order to manufacture the upper and side segments of mutually different cross-section, it has been a conventional practice to prepare and use two kinds of exchangeable extrusion dies, one for the upper segments and the other for the side segments, which are expensive and make it thus difficult to reduce the production cost of the molding members. Not only the exchange of the dies requires troublesome and time-consuming manual operations, but also it is necessary, after the exchange of the die and commencement of extrusion of synthetic resin material therefrom, to wait for some time until the die begins to stably extrude a continuous body with a desired accuracy of the cross-section.
Alternate use of different dies to produce different segments of basically same cross-section thus proved to be quite disadvantageous in many cases, particularly when a relatively small number of segments of various cross-sections are to be produced in each production lot. Moreover, the use of separate corner segments for connecting the upper and side segments with each other increases the production cost, and may often result in the formation of connection lines between the upper and corner segments and also between the corner and side segments, and hence in an undesirable degradation of the appearance.